A label that could be printed and erased fifty times or more, would be very useful for certain applications. One obvious application is the return due date associated with library materials. Libraries currently use several methods to indicate the date when a borrowed item is due to be returned. Some libraries print the due date on a slip of paper, which is handed to the patron. If the patron checks out more than one item, they will all be listed on the one paper. There are three disadvantages to this system. First, it consumes paper. Second, the due date information is separate from the borrowed item. The patron is unable to simply look on the book they are currently using, to determine its due date. Third, the small piece of paper is easily lost. Another method that has been used for years is to stamp or write the due date on a card. This card is then placed in a envelope attached to the book. This is a very time consuming method. The envelope is usually inside of the book. So, the book must be opened and then the card is removed. The date is then written or stamped onto the card. The card is then replaced into the envelope and the book closed. All of this handling is time consuming and costly for the libraries. The cards and envelopes are costly to purchase and further costs are incurred in replacing the cards when they are full or lost. Plus, there is the additional cost of mounting the envelopes in the books.
A third method uses a small label with the due date printed on it. These are applied directly to the book cover. A label applicator is used that both prints and applies each label. These applicators are hand operated. The librarians must squeeze the handle of the device for every item that they check out. This has resulted in some library workers now having repetitive motion injuries. Another disadvantage is the pile of labels that accumulate on popular books. Sometimes it becomes unclear, on which of these labels is the real due date? Periodically the mess of labels on the cover must be scrapped off. In an attempt to solve the confusion and mess, a new product has been developed. This is a special label that is applied to the cover. Printed on this label are boxes for placing the smaller due date labels. This allows the smaller labels to be applied in order and eliminates the confusion. After the special label is full it can be peeled off and replaced. This product solves the confusion problem, but at a cost. First, there is the cost of the these additional labels, applying them, and removing them. Then, there is the hidden cost of the added time required to apply each due date label accurately on the special label.
A new method, that only requires a single label to provide due date information, is disclosed in U.S. Pat. No. 5,290,066 Mody (1994). Mody's label is reprintable. The label is made from a special plastic sheet which is called Particle Oriented Paper (POP). Particles within the plastic sheet can be oriented by the application of magnetic fields. Depending on the resulting orientation of the particles, portions of the sheet will appear darker or lighter. Properly applied the magnetic fields can be used to print information onto POP. Magnetic fields are also used to erase the information from the POP. POP is commercially available from Eurand America, Inc. On testing a sample of POP provided by Eurand America, it was found that a magnetic field did darken it. But I found there was not much difference in contrast between the darkened (printed) and undarkened (unprinted) areas on the standard color POP provided by Eurand. This is because the standard color of POP is already a dark color, medium dark green. Used as a due date label, the date would be readable, but it certainly would not stand out. A second disadvantage of POP, is its present high cost. In quantities of five hundred square feet, it is priced by Eurand America at $9.50 per square foot.
The required use of magnetic fields for printing and erasing may be a disadvantage for using POP labels in another application. Mody (U.S. Pat. No. 5,290,066) describes using POP reusable labels in the video tape rental market. Some video stores allow different rental periods for different video titles. Returning the video just one day late will double the customers cost of the rental. The customer would obviously appreciate having the due date printed on these videos. Mody suggests using POP labels for this application. But he does not address the possible problem that might occur when erasing and printing POP labels. As previously stated, magnetic fields are used to erase and print POP labels. Magnetic fields are also used to erase and record on video tapes. The unanswered question is: could the erasing and printing of the POP label, erase or degrade the video recordings? If the answer is yes, then; the videos would need to be kept way from the magnetic fields of the POP label printers. A video tape would first have to be removed from its box before the POP label on the box could be erased and printed. Then the video could be replaced in the box. If these extra check out steps were necessary, that would be another disadvantage for POP labels. Mody provides no information on this potential problem of using POP labels in the video tape market.
In the preceding description of the limitations of the prior art, only library book and video tape rental applications have been discussed. They are only an example of the types of materials and situations requiring the temporary display of information. The scope of this patent should not be construed to be limited to library books and video tapes. For instance, further uses for labels that provide erasable and reprintable displays of information clearly exist in manufacturing and retailing. Products being manufactured are sometimes moved through the process in tubs, on carts or on pallets et cetera. It can be useful to have temporary information like part numbers, quantities, or work order information on the material handling device. A reusable label attached to the material handling device would provide a convenient place to display this information. Another useful area for reusable labels is in inventories. Manufacturer's, wholesaler's, and retailer's inventories are constantly changing. Reusable labels attached to shelves and bins could provide an inexpensive and convenient place to display the quantities of items in inventory. A further application could be in the display of prices of retail products. Product prices are also continually changing, especially in the grocery market. An attractive label with printed product description and a separate reprintable area for price information may offer cost savings in this application.